Facebook’s Oculus patented an eye tracking technique which uses light field cameras inside the headset. Most previous eye tracking systems used a regular or infrared camera combined with an IR illuminator to keep the eyes lit.

A light field camera differs from a regular camera in that it also captures the direction that light is travelling. This directional information can be used to understand the depth of the image, and thus 3D shape of the eye, instead of just the color and brightness. By knowing the 3D shape of the eye, the system can find out where the pupil is relative to the eye itself, and thus a more accurate estimation of the user’s gaze direction than with just the apparent 2D shape of the pupil.

Foveated rendering should one day enable much higher resolution VR headsets without requiring an expensive top of the line graphics card.